This is not reingold-tilford. The algorithm has two parts. The first part is a heuristic to distribute nodes into multiple layers when it won't fit in one. Then

This is not reingold-tilford. The algorithm has two parts. The first part is a heuristic to distribute nodes into multiple layers when it won't fit in one. Then for each layer, it is a physics simulation with the labels. Each label has attraction force to the desired position, but they also push each other.